The present invention generally relates to monitoring and control of rotating machinery and, more particularly, to a system and method for performing error correction in rotor position signals received from angular position sensors, such as resolvers.
Many vehicle drive systems, such as those present in electric and hybrid vehicles, use a rotating electric machine, such as a permanent magnet (PM) machine, to help direct power to the vehicle transmission and wheels. In order to accurately and efficiently perform dynamic torque control of the rotating electric machine, an angular position sensor is typically used to determine the angular position of the rotor. The position sensor, which often comprises a rotating electrical transformer device known as a resolver, is susceptible to a variety of error sources that can reduce the overall system performance. For example, mechanical errors can be introduced when centering the rotor of a resolver relative to its stator during assembly. In addition to mechanical tolerances, errors can be introduced during the processing of the position sensor output signals, such as when the finite bandwidth of an analog-to-digital converter changes the spectral behavior of the signals.
In certain applications, the system is designed to accept such error and the resulting reduction in performance is tolerated. If the reduction in performance is not permissible, digital filtering techniques can be used to attempt to filter the error. However, known filtering techniques are often inadequate and may cause additional undesirable phase shift and lag effects.
An improved technique for correcting errors in the position sensor output is therefore needed which will dynamically learn the position error associated with a position sensor and correct for such error when the system is used in its intended application.